1. Field of the Invention
The present invention relates to cooling of electronic assemblies, and more specifically to a heat sink assembly retainer for electronic components such as transistors, integrated circuits or the like which are mounted on a printed circuit board (PCB) of electronic devices.
2. Background of the Related Art
Since the successful introduction of integrated circuits (ICs), there has been a steady progression toward larger IC devices with capability for a greater number and scope of functions. Heat produced by these larger semiconductors devices is conventionally removed by heat sinks, which dissipate the heat through either natural air convection or by powered ventilation.
When attaching a heat sink to the heat-generating electronic device, it is usually not desirable to use bonding such as by way of adhesive. This is because of the permanency of such attachment. If a semiconductor device has to be discarded due to malfunction, it is not desirable to throw away the heat sink too. Thus it is generally desirable to attach a heat sink to a chip or device by mechanical means such as a retainer clip. Typical heat sinks currently in use comprise a flat plate generally the same size as the device, and a plurality of radiation fins extending upwardly from the flat plate. The heat sink is commonly manufactured by extrusion and subsequent machining.
A new development in the art of electronic packages for microprocessor semiconductor devices utilizes a cartridge, which contains a printed circuit board on which the microprocessor is mounted. The cartridge may be made of metal. At least one major microprocessor supplier has established a specification for the cartridge, which includes a thermal plate. To facilitate proper attachment of the heat sink to the cartridge thermal plate, the thermal plate is provided with multiple openings to permit engagement of retainer clips accompanying the heat sink.
A wide variety of heat sink assemblies and retainers are available. For example, the applicant""s earlier U.S. Pat. No. 5,600,540 shows a heat sink and retainer for electronic integrated circuits comprising a two-piece retainer clip particularly adapted for use in connection with a semiconductor device mounted directly on a socket, which in turn is attached to a printed circuit board. Another device is shown in the applicant""s earlier U.S. Pat. No. 5,208,731, which discloses a single-piece retainer, clips for a similar chip, a socket and a heat sink assembly. Another device is shown in U.S. Pat. No. 5,448,449. It has either one or two retainer clips for securing a heat sink to a semiconductor chip, which is mounted in a socket.
In all the above-described devices, laborious operation is required to properly attach the retainer clip and secure the heat sink to the semiconductor chip and/or socket. This significantly reduces the cost effectiveness of a retainer clip. It is also desired to have a retainer clip with positive and easily ascertainable engagement means. A retainer clip should only be able to exist in two states: attached or detached. If an intermediate state is permitted, the assembly may not be completely attached yet pass unnoticed by a user performing the attachment operation. If so, when the computer or other electronic device is shipped and subjected to various forces such as vibration, the retainer clip may be loosened and the heat sink may become disengaged. If the device continues to be subjected to rough handling during shipping, damage to other components within the electronic device may also result. A dislodged heat sink undetected by a user will likely result in the semiconductor device easily overheating and getting damaged or destroyed.
Another problem with conventional retainer clips again relates to rough handling that frequently occurs during shipping of electronic devices which contain a semiconductor device, heat sink and retainer clip. It is of course desirable that a retainer clip exerts a relatively uniform and large pressure on a heat sink, so that a lower flat base of the heat sink is in intimate thermal engagement with an upper surface of the chip or with a module plate (see above). This pressure creates frictional engagement between these two surfaces. However, a sharp blow coplanar with such surfaces can cause the heat sink to slide relative to the chip. The heat sink may strike the retainer clip assembly, causing the retainer clip to become dislodged and the heat sink to be separated from the chip. Even partial displacement of the heat sink base relative to the semiconductor device will affect the efficiency of heat transfer from the device to the heat sink.
Accordingly, an object of the present invention is to provide an improved retainer device for a heat sink assembly used for an electrical component mounted on a printed circuit board of an electronic device.
Another object is to provide a retainer device which is simple in construction, easy to use, efficient and effective in removing heat from the electrical component.
These and other objects can be achieved by a heat sink assembly retainer constructed according to the principles of the present invention and adapted to be mounted on a printed circuit board for dissipating heat from a heat-generating component of an electronic device. The heat sink assembly retainer comprises a retainer device for attachment of a heat sink to an electronic package or semiconductor device. The heat sink comprises a flat base with a plurality of upwardly extending fins. The fins are defined at least one channel. The retainer device comprises an operation lever, a fastening frame, and a backing plate with a plurality of upwardly extending clasp hooks. The backing plate is attached to a bottom surface of a motherboard of an integrated circuit module. The fastening frame is positioned around the periphery of the heat-dissipating device, and limits displacement of the heat sink. The clasp hooks of the backing plate hold the fastening frame in place. The fastening frame has pivot openings, cam plates, and cutouts at bottom portions of the cam plates. The operation lever includes an operational body a pair of arms, a pair of urging portions, and a pair of pivot axles passing through the pivot openings of the fastening frame. The operational body is rotated to make the urging portions pass around the cam plates until the urging portions are snapped into the cutouts. The fastening frame elastically deforms and causes the urging portions to press against the heat sink. The heat sink is thereby pressed tightly against the printed circuit board module.